Backrest and adjustable arm for a chair

ABSTRACT

A chair having a backrest with a Y-shaped member. The member being affixed to the center of the top rail of the backrest frame at one end. The other end of the Y-shaped member is connected to backrest fabric, pulls it rearward, and hold the backrest fabric in tension using a pair of retractors. The backrest fabric is secured to the retractors by a weld cord contained with in a chamber formed in each retractor. The weld cord is sewn into a fabric sheath that is, in turn, stitched to the backrest fabric. The member is biased to flex rearward when the backrest fabric moves rearward from an at-rest position.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional patentapplication No. 60/297,812.

BACKGROUND OF THE INVENTION

The invention relates generally to chairs, and more particularly to aretractor structure for a chair backrest and a height-adjustable chairarm.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction withthe appended drawing figures wherein like numerals denote like elements.

FIG. 1 is a perspective view of a chair showing the backrest andadjustable arm of the present invention.

FIG. 2 is an enlarged perspective view of the right arm.

FIG. 3 is an enlarged perspective view of the armrest frame for theright arm.

FIG. 4 is an exploded view, taken from the right-front side, of theright arm.

FIG. 5 is an exploded view, taken from the right-rear side, of the leftarm.

FIG. 6 is a partial view of the lower portion of the retractor structureof the backrest.

FIG. 7 is an enlarged front partial view of the barrel portion of theretractor structure.

FIG. 8 is a sectional view of the retractor structure shown in anextended position (in tension).

FIG. 9 is a sectional view of the retractor structure shown in aretracted position (tension relieved).

FIG. 10 is a perspective view of one assembled pull and plunger.

FIG. 11 is a partial sectional view of the male pull.

FIG. 12 is a partial sectional view of the female pull and plunger.

FIG. 13 is a perspective view of the welt cord and enveloping fabric.

FIG. 14 is an end view showing the welt cord and fabric sheath with thefabric sheath is sewn to the backrest fabric.

FIG. 15 is an end view showing the welt cord contained within theassembled male and female pulls.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The ensuing detailed description provides preferred exemplaryembodiments only, and is not intended to limit the scope, applicability,or configuration of the invention. Rather, the ensuing detaileddescription of the preferred exemplary embodiments will provide thoseskilled in the art with an enabling description for implementing thepreferred exemplary embodiments of the invention. It being understoodthat various changes may be made in the function and arrangement ofelements without departing from the spirit and scope of the invention,as set forth in the appended claims.

To aid in describing the invention, directional terms are used in thespecification and claims to describe portions of the chair 10 of thepresent invention (e.g., upper, lower, left, right, etc.). Thesedirectional definitions are merely intended to assist in describing andclaiming the invention and are not intended to limit the invention inany way. In addition, reference numerals that are introduced in thespecification in association with a drawing figure may be repeated inone or more subsequent figures without additional description in thespecification in order to provide context for other features.

FIG. 1 shows a preferred embodiment of the chair 10 of the presentinvention, which includes a base 12, a seat 14, left and right arms 16,18 and a backrest 20. The base 12 and seat 14 are conventional. Thebackrest 20 defines an opening that is covered by a backrest fabric,which is preferably an expanded mesh material that is see-through. Itshould be understood that any features described in relation to theright arm 18 are also present as a mirror image in the left arm 16 andvice-versa.

Referring now to FIG. 2, the right arm 18 includes an armrest 22 and anarm support 24, which is connected to the armrest 22 by aheight-adjustment structure 26. As will be discussed in greater detailherein, the armrest 22 is height-adjustable relative to the seat 14. Thearmrest support 24 includes a lateral portion 23 that is rigidly affixedto the base 16 and an upright portion 25 that extends upwardly from thelateral portion 23. Rigidity for the armrest 22 is provided by anarmrest frame 30 (see FIG. 3), which is connected to theheight-adjustment structure 26 via a bracket 32.

Referring now to FIGS. 4 and 5, the height-adjustment structure 26 willnow be described in detail. The armrest 22 is connected to the support24 by two linkages 44, 46. The linkages 44, 46 pivot relative to thesupport 24 and the armrest frame bracket 32 (see FIG. 3), so that thearmrest maintains a substantially level (i.e., remains in substantiallythe same rotational orientation) as the linkages 44, 46 move the armrest22 up and down through the armrest's 22 range of motion. In thisembodiment, the linkages 44,46 are of equal length and are arranged toremain parallel when pivoting. Linkage 44 will be referred to herein asthe drive linkage 44 and linkage 46 will be referred to herein as thenon-drive linkage 46. This portion of the height-adjustment structure 26is sometimes referred to in the art as a four-bar linkage.

The linkages 44, 46 are sandwiched between a boss plate 48 and thesupport 24 and are pivotally attached to the boss plate 48 by linkageposts 50, 52 located on the inner side of the boss plate 48. The linkagepost 50 for the drive linkage 44 is preferably located along a centralaxis C of the height-adjustment structure 26 and the linkage post 52 forthe non-drive linkage 46 is located above the linkage post 50 for thedrive linkage 44 and vertically aligned therewith. A third post 54 isincluded to provide stability. Each of the three posts 50, 52, 54 isaligned with a respective hole located in the support 24 and is securedto the support 24 with a screw or any other suitable fastener. The outerdiameter of each of the linkage posts 50, 52 is sized to allow a lowerhole of the respective linkage 44,46 to rotate about the post, whileminimizing “play” in the linkage 44, 46. Similarly; the length of eachof the posts 50, 52, 54 is sized to allow the linkages 44, 46 to rotatefreely about the posts 50, 52, while minimizing “play” fromside-to-side.

An eccentric shaft 56 is located on the outer side of the boss plate 48.Moving from the outside end to the inside end, the eccentric shaft 56includes a gear 58 that engages a knob 28, a non-eccentric bearingsurface 60 that rotates within a bearing plate 64, and an eccentricbearing surface 62 that rotates within an axial hole 65 of an inner gear66. Both bearing surfaces 60, 62 are cylindrical in shape. Thenon-eccentric bearing surface 60 is centered about the central axis Cand the eccentric bearing surface 62 is off-center from the central axisC. In this embodiment, the eccentric bearing surface 62 is off-center byabout 0.070 inches.

Six posts 68 extend outwardly from the boss plate 48. Each of the sixposts 68 is located along a circular path and is evenly-spaced along thepath. Both the bearing plate 64 and the inner gear 66 include six holesformed therein that are positioned and spaced to slide over the sixposts 68 in the boss plate 48 so that the bearing plate 64 and the innergear 66 cannot rotate relative to the boss plate 48. Each of the sixholes located in the inner gear 66 is 0.070 inches larger in radius thaneach of the posts 68 to allow lateral movement of the inner gear whenthe eccentric shaft 56 is rotated. In this embodiment, lateral movementof the inner gear 66 follows a circular path as the eccentric shaft 56is rotated. An outer gear 70 is sandwiched between the bearing plate 64and the boss plate 48.

The inner gear 66 includes outwardly-extending teeth (i.e., extendingaway from the central axis C) teeth and is positioned inside the outergear 70, which has inwardly-extending teeth (extending inwardly towardthe central axis C). The inner gear 66 has one less tooth than the outergear 70. In this embodiment, the inner gear has twenty-three (23) teethand the outer gear has twenty-four (24) teeth. In this embodiment all ofthe teeth have a depth of 0.120 inches.

When the eccentric shaft 56 is rotated a full revolution (i.e., 360degrees), the eccentric bearing surface 62 moves the inner gear 66through one cycle of lateral movement, which causes the outer gear torotate the width of one tooth (about fifteen degrees in thisembodiment). The outer gear 70 includes a slot 72 that engages the drivelinkage 44. Thus, rotation of the outer gear 70 causes the drive linkage44 to rotate in the same direction. This structure also provides amechanical advantage between rotation of the knob 28 and change inheight of the armrest 22.

As noted above, the larger relative size of the post-engaging holes ofthe inner gear 66 allows lateral movement of the inner gear 66 relativeto the outer posts 68 of the boss plate 48. The magnitude of thedifference in radius between the post-engaging holes of the inner 66 andthe outer posts 68 of the boss plate is equal to the offset of theeccentric bearing surface 62 and is equal to 50-55% of the tooth depthof the inner gear 66. This enables sufficient lateral movement of theinner gear 66 to allow the teeth of the inner gear 66 to engage anddisengage the teeth of the outer gear 70 as the eccentric shaft 56 isrotated. In addition, it ensures that at least one of the outer posts 68will be engaged with the wall of the post-engaging hole located therein.This minimizes rotation of the inner gear 66 and enables the inner gear66 “bind”, which prevents rotation of the outer gear 70 when theeccentric shaft 56 is not being rotated by the knob 28.

Optionally, the one of the arms 16, 18 may include a seat heightadjustment lever 27 pivotally attached to the support 24 and curved tofollow the curvature of the outer surface of the arm height adjustmentknob 28. This allows the user to more easily access the seat heightadjustment lever 27 than with conventional levers which are locatedunder the seat.

Most of the components of the height adjustment structure 26 are formedof metal or a durable, rigid polymer. Smooth and reliable operation hasbeen achieved by forming the bearing plate 64, inner gear 58 and outergear 60 from nylon, Delrin® brand plastic, manufactured by E.I. DuPontNemours and Company, or other rigid, non-binding polymers.

Referring now to FIGS. 1 and 6, the backrest 20 will be described ingreater detail. The backrest 20 includes a top rail 27 having aninverted Y-shaped member 74 that is attached to the top rail 27 at anupper end 77 and terminates at two lower ends 76, 78. A retractor 80, 82is located on the inner side of each of the lower ends 76, 78. The leftand right retractors 80, 82 work in conjunction with the Y-shaped member74 to pull the backrest fabric (the fabric against which rests the backof a person sitting in the chair) rearward along two seams. As will beexplained herein, the retractor 80, 82 places the backrest fabric undertension, which provides a firm, comfortable surface for the user. Inaddition, the retractor 74 is designed to “give”, which adds to thecomfort of the user. The Y-shaped member 74 may also flex slightly toprovide additional “give” to the backrest fabric.

In the context of the parts of the backrest 20, including backrestfabric 122, the Y-shaped member 74 and the retractors 80,82, the terms“front,” “frontward” or “front side” are intended to refer to the sideof any of these parts which faces a person sitting in the chair.Conversely, the terms “rear,” “rearward” or “rear side” are intended torefer to the side of any of the parts of the backrest 20 opposite thefront side (i.e., facing way from a person sitting in the chair).

The left and right retractors 80, 82 are mirror-images of each-other. Itshould be understood that any features described in relation to the leftretractor 80 are also present as a mirror image in the right retractor82 and vice-versa. The retractor 80 includes a pull 84, a plunger 86 anda barrel 88.

Referring now to FIGS. 4 and 5, one can see that the pull 84 is slenderand elongated. The inner edge of the pull 84 has a slight concavecurvature of radius R, where R is between 20 and 30 inches, preferably24 inches. This curvature is intended to more closely follow the naturalcurvature of the user's back, and therefore, make the backrest 20 morecomfortable. The plunger 86 is affixed to the outer surface of the pull84, preferably midway between the top and bottom of the pull 84. Theplunger 86 includes a base 92 which engages the pull 84, a slender,cylindrical body 94 and a tapered head 90 that is designed to beinserted through a radial array of fingers 96 (see also FIG. 7). Thefingers 96 flex outwardly as the head 90 is pushed through, then returnto their original position. A lip 96 that defines the transition betweenthe head 90 and the body 94 prevents the head 90 from being pulled backthrough the fingers 96.

In the extended position shown in FIG. 8, the retractor 80 keeps thebackrest fabric under tension. This tension is provided by biasing theY-shaped member 74 rearward from the tensioned position. As used in thespecification and claims, the terms “tensioned position” or “at-restposition” is meant to describe a position in which the chair 10 is fullyassembled, but no external loads (such as that of a person leaningagainst the backrest 20) are being applied to the backrest fabric otherthan those imposed by the backrest frame 21 and the Y-shaped member 74.The amount of tension applied to the backrest fabric in the tensioned orat-rest position will depend upon the type of chair and intended userheight and weight ranges. When a user begins to lean back against thebackrest fabric 122, the lower ends 76,78 of the Y-shaped member 74 moverearwardly until the Y-shaped member is no longer biased. This will bereferred to as a “partially loaded position.” If additional rearwardforce is applied against the backrest fabric 122, the retractor 80 canalso move rearwardly, or “give”, as shown in FIG. 9. This will bereferred to as a “retracted position.”

In this embodiment, the pull 84 is comprised of two haves: a male half98 and a female half 100, as shown in FIGS. 10-12. Use of male andfemale halves 98, 100 simplifies assembly. The male and female halves98, 100 include structures to retain the plunger 86, in this embodimentmating half-cylinders 102, 104 each having a centrally locatedhalf-circle 106, 108 are provided. Alternatively, the plunger 86 couldbe molded as part of one of the male and female halves 98, 100. Inaddition, the male and female halves 98, 1 00 include a fasteningstructure that prevents the halves 98, 1 00 from separating onceassembled. In this embodiment latches 110 located along the male half 98mate with locks 112 located along the female half 100. Any suitablefastening structure could be used, as could adhesives (either alone oras a supplement to the fasteners).

Referring now to FIGS. 13-15, the structure for attaching the backrestfabric to the retractor is shown. A fabric sheath 116 is sewn around awelt cord 114, leaving a flap 118 of excess fabric. The welt cord 114 ispreferably slightly shorter in length than the pull 84 and mayoptionally have the same curvature (or radius R) as the inner surface ofthe pull 84. The welt cord 114 is preferably formed of a polymericmaterial that will provide some longitudinal flexibility, but strongcross-sectional rigidity. The fabric sheath 116 is preferably a durablefabric having a dense weave.

The fabric sheath 116 is sewn to backrest fabric 122 along a seam 120that is located where the welt cord 114 and fabric flap 118 meet. Afterthe backrest fabric 122 is sewn to the fabric sheath 116, the welt cord114 and fabric sheath 116 are enclosed within a chamber 124 formedwithin the pull 84. Preferably, the welt cord 114 is drawn into thechamber 124 sufficiently far so that the seam 120 cannot be felt by theuser.

When being assembled, the welt cord 114 and fabric sheath 116 areinserted into the chamber 124, then the male and female halves 98, 100are assembled. An elongated slot 126 (see also FIG. 6) allows the maleand female halves 98, 100 to be more easily assembled and preventspinching of the backrest fabric 122.

Optionally, an opaque fabric member can be provided which is positionedin front of the backrest fabric 122. The opaque fabric member ispreferably sewn to the backrest fabric 122 around its perimeter andalong or near the seam 120 which attaches that backrest fabric 122 tothe fabric sheath 116. The opaque member is designed to provideadditional padding, and a more traditional appearance from the font sideof the chair 10. The opaque fabric member could be formed from anyconventional material, such as padded core sandwiched between layers ofa polyester or polyester-blend material.

While the principles of the invention have been described above inconnection with preferred embodiments, it is to be clearly understoodthat this description is made only by way of example and not as alimitation of the scope of the invention.

1. A backrest for a chair, the backrest comprising: a backrest framethat defines an opening; a backrest fabric that is attached to thebackrest frame and covers the opening; and a member having a first endthat is attached to the backrest frame and a second end that is distalto the first end and is connected to the backrest fabric, the memberbeing biased to pull the backrest fabric rearward so that the backrestfabric is in tension when in an at-rest position.
 2. The backrest ofclaim 1, wherein the backrest frame includes a top rail and the firstend of the member is attached to the top rail.
 3. The backrest of claim1, wherein the member comprises a Y-shaped member.
 4. The backrest ofclaim 1, wherein the backrest further comprises a retractor attached tothe second end of the member and the backrest fabric is secured to theretractor.
 5. The backrest of claim 4, wherein the backrest fabric issecured to the retractor by a welt cord contained within a fabric sheaththat is attached to the backrest fabric, the welt cord being retainedwithin a chamber located in the retractor.
 6. The backrest of claim 4,wherein the retractor is elongated an includes a concave surface thatcontacts the rear surface a rear side of the backrest fabric.
 7. Thebackrest of claim 1, wherein the backrest fabric comprises an expandedmesh.
 8. The backrest of claim 1, further comprising an opaque fabricpositioned on the front side of the backrest fabric.
 9. The backrest ofclaim 1, wherein the second end of the member is biased to move rearwardwhen the backrest fabric is moved rearward from the at-rest position.10. A chair comprising: a seat; a base; a backrest frame, the backrestframe defining an opening; a backrest fabric that is attached to thebackrest frame and covers at least a portion of the opening; and amember having a first end that is attached to the backrest frame and asecond end that is distal to the first end and is connected to thebackrest fabric, the member being biased to pull the fabric rearward sothat the backrest fabric is in tension when in an at-rest position, themember being biased to flex rearward when the backrest fabric is movedrearward relative to the at-rest position.
 11. The chair of claim 10,wherein the backrest frame comprises a top rail and the first end of themember is attached to the top rail.
 12. The chair of claim 10, whereinthe first end of the member is attached to the center of the top rail.13. (canceled)
 14. The chair of claim 10, wherein the member is aY-shaped member having a third end that is distal to the first end andis connected to the backrest fabric.
 15. The chair of claim 14, whereinthe backrest frame comprises a top rail and the first end of theY-shaped member is attached to the top rail.
 16. A chair comprising: aseat; a base; a backrest frame defining an opening; a backrest fabricthat covers at a least a portion of the opening; and a Y-shaped memberhaving a first end that is attached to the backrest frame and second andthird ends that are both distal to the first and are connected to thebackrest fabric.
 17. The chair of claim 16, wherein the backrest framecomprises a top rail and the first end of the Y-shaped member isattached to the top rail.
 18. The chair of claim 17, wherein theY-shaped member is attached to the center of the top rail.
 19. The chairof claim 18, wherein the Y-shaped member further comprises a retractorattached to the second end of the member and the backrest fabric issecured to the retractor.
 20. The backrest of claim 19, wherein thebackrest fabric is secured to the retractor by a welt cord containedwithin a fabric sheath that is attached to the backrest fabric, the weltcord being retained within a chamber located in the retractor.
 21. Thebackrest of claim 19, wherein the retractor is elongated and includes aconcave surface that contacts the rear surface of the backrest fabric.